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the processes leading to the deformation and destruction of planets spiraling into the convective envelope of their host stars are described. the planet is compressed by ram pressure and deformed into a flattened shape, for which a quantitative model is developed. compression increases the planet’s density contrast wit... | disruption of a planet spiraling into its host star |
context. the dissipation of the kinetic energy of wave-like tidal flows within the convective envelope of low-mass stars is one of the key physical mechanisms that shapes the orbital and rotational dynamics of short-period exoplanetary systems. although low-mass stars are magnetically active objects, the question of ho... | does magnetic field impact tidal dynamics inside the convective zone of low-mass stars along their evolution? |
context. rotational shear in sun-like stars is thought to be an important ingredient in models of stellar dynamos. thanks to helioseismology, rotation in the sun is characterized well, but the interior rotation profiles of other sun-like stars are not so well constrained. until recently, measurements of rotation in sun... | limits on radial differential rotation in sun-like stars from parametric fits to oscillation power spectra |
solar modelling has long been split into ''internal'' and ''surface'' modelling, because of the lack of tools to connect the very different scales in space and time, as well as the widely different environments and dominating physical effects involved. significant efforts have recently been put into resolving this disc... | global mhd simulations of the solar convective zone using a volleyball mesh decomposition. i. pilot |
the sun has a near-surface shear layer (nssl), within which the angular velocity decreases rapidly with radius. we provide an explanation of this layer based on the thermal wind balance equation. since convective motions are not affected by solar rotation in the top layer of the convection zone, we argue that the tempe... | a theoretical model of the near-surface shear layer of the sun |
internal gravity waves (igw) propagate in the radiation zones of all stars. during propagation, their amplitudes are affected by two main features: radiative diffusion and density stratification. we have studied the implications of these two features on waves travelling within the radiative zones of non-rotating stars ... | onset of non-linear internal gravity waves in intermediate-mass stars |
context. solar twins are increasingly the subject of many studies owing to their wide range of applications from testing stellar evolution models to the calibration of fundamental observables; these stars are also of interest because high precision abundances could be achieved that are key to investigating the chemical... | serendipitous discovery of the faint solar twin inti 1 |
the k-ω model for turbulence was first proposed by kolmogorov. a new k-ω model for stellar convection was developed by li, which could reasonably describe turbulent convection not only in the convectively unstable zone, but also in the overshooting regions. we revised the k-ω model by improving several model assumption... | applications of the k-ω model in stellar evolutionary models |
this paper considers the dominant dynamical, thermal and rotational balances within the solar convection zone. the reasoning is such that: coriolis forces balance pressure gradients. background vortex stretching, baroclinic torques and nonlinear advection balance jointly. turbulent fluxes convey what part of the solar ... | the rotational influence on solar convection |
we present here a detailed calculation of opacities for fe xvii at the physical conditions corresponding to the base of the solar convection zone. many ingredients are involved in the calculation of opacities. we review the impact of each ingredient on the final monochromatic and mean opacities (rosseland and planck). ... | quantitative comparison of opacities calculated using the r-matrix and distorted-wave methods: fe xvii |
convective motions extend beyond the nominal boundaries of a convection zone. these motions mix fluid through multiple mechanisms collectively called "convective boundary mixing." in this note, we discuss three distinct fluid dynamical processes: convective overshoot, entrainment, and penetrative convection. we describ... | convective boundary mixing processes |
context. lithium and beryllium are destroyed at different temperatures in stellar interiors. as such, their relative abundances offer excellent probes of the nature and extent of mixing processes within and below the convection zone.aims: we determine be abundances for a sample of eight solar twins for which li abundan... | shallow extra mixing in solar twins inferred from be abundances |
we explore the general properties of near-surface flows around solar active regions. helioseismic holography is applied to hmi dopplergrams yielding nearly 5000 flow measurements of 336 unique active regions observed by the solar dynamics observatory between 2010 and 2014. ensemble averages of the flows, over subsets o... | flows around averaged solar active regions |
we discuss the influence of rotation on the combined synthesis of {}44{ti} and {}56{ni} in massive stars. while {}56{ni} is significantly produced by both complete and incomplete explosive si burning, {}44{ti} is mainly produced by complete explosive si burning, with a minor contribution (in standard non-rotating model... | the synthesis of 44ti and 56ni in massive stars |
convection and turbulence in core-collapse supernovae (ccsne) are inherently three-dimensional (3d) in nature. however, 3d simulations of ccsne are computationally demanding. thus, it is valuable to modify simulations in spherical symmetry to incorporate 3d effects using some parametric model. in this paper, we report ... | general relativistic neutrino-driven turbulence in one-dimensional core-collapse supernovae |
the main object of the paper is to present the condition of the nondiffusive part of the reynolds stress for driving the double-cell structure of the solar meridional circulation, which has been revealed by recent helioseismic observations. by conducting a set of mean-field hydrodynamic simulations, we confirm for the ... | double-cell-type solar meridional circulation based on a mean-field hydrodynamic model |
linear damping rates and modal frequency corrections of radial oscillation modes in selected legacy main-sequence stars are estimated by means of a non-adiabatic stability analysis. the selected stellar sample covers stars observed by kepler with a large range of surface temperatures and surface gravities. a non-local,... | damping rates and frequency corrections of kepler legacy stars |
in recent years, a revised set of solar abundances has led to a discrepancy in the sound-speed profile between helioseismology and theoretical solar models. conventional solutions require additional mechanisms for energy transport within the sun. vincent et al. have recently suggested that dark matter with a momentum o... | effect of electromagnetic dipole dark matter on energy transport in the solar interior |
coronal extreme-ultraviolet (euv) waves are large-scale disturbances propagating in the corona, whose physical nature and origin have been discussed for decades. we report the first three-dimensional (3d) radiative magnetohydrodynamic simulation of a coronal euv wave and the accompanying quasi-periodic wave trains. the... | exploring the nature of euv waves in a radiative magnetohydrodynamic simulation |
overshooting of turbulent motions from convective regions into adjacent stably stratified zones plays a significant role in stellar interior dynamics, as this process may lead to mixing of chemical species and contribute to the transport of angular momentum and magnetic fields. we present a series of fully nonlinear, t... | on the dynamics of overshooting convection in spherical shells: effect of density stratification and rotation |
the non-equilibrium property of turbulence modifies the characteristics of turbulent transport. with the aid of response function formalism, such non-equilibrium effects in turbulent transport can be represented by the temporal variation of the turbulent energy (k) and its dissipation rate (ɛ) along the mean stream thr... | non-equilibrium turbulent transport in convective plumes obtained from closure theory |
in this paper, we investigate the upward overshooting by three-dimensional numerical simulations. we find that the above convectively stable zone can be partitioned into three layers: the thermal adjustment layer (mixing both entropy and material), the turbulent dissipation layer (mixing material but not entropy), and ... | upward overshooting in turbulent compressible convection. i. effects of the relative stability parameter, the prandtl number, and the péclet number |
context. the ratio of kinematic viscosity to thermal diffusivity, the prandtl number, is much smaller than unity in stellar convection zones.aims: the main goal of this work is to study the statistics of convective flows and energy transport as functions of the prandtl number.methods: three-dimensional numerical simula... | prandtl number dependence of stellar convection: flow statistics and convective energy transport |
we present results of realistic three-dimensional (3d) radiative hydrodynamic simulations of the outer layers of a moderate-mass star (1.47 m ⊙), including the full convection zone, the overshoot region, and the top layers of the radiative zone. the simulation results show that the surface granulation has a broad range... | dynamics of turbulent convection and convective overshoot in a moderate-mass star |
we compute rotating 1d stellar evolution models that include a modified temperature gradient in convection zones and criterion for convective instability inspired by rotating 3d hydrodynamical simulations performed with the music code. in those 3d simulations we found that convective properties strongly depend on the s... | suppression of lithium depletion in young low-mass stars from fast rotation |
the 2d internal rotation of kic 11145123 has been inferred via asteroseismology. based on the optimally localized averaging method and a simple three-zone modeling of the internal rotation, we have found evidence for a contrast between the internal rotation of the radiative region and that of the convective core; the r... | the two-dimensional internal rotation of kic 11145123 |
context. studies of stellar convection typically use a spherical-shell geometry. the radial extent of the shell and the boundary conditions applied are based on the model of the star investigated. we study the impact of different two-dimensional spherical shells on compressible convection. realistic profiles for densit... | spherical-shell boundaries for two-dimensional compressible convection in a star |
hydrostatic models of wolf-rayet (wr) stars typically contain low-density outer envelopes that inflate the stellar radii by a factor of several and are capped by a denser shell of gas. inflated envelopes and density inversions are hallmarks of envelopes that become super-eddington as they cross the iron-group opacity p... | on the launching and structure of radiatively driven winds in wolf-rayet stars |
context. libraries of stellar models computed with either the ledoux or the schwarzschild criterion to determine the sizes of convective regions are available in the literature. it is still not clear, however, which of these two criteria should be used, although many works have been devoted to that question in the past... | the impact of convective criteria on the properties of massive stars |
the prevalence and consequences of convection perpendicular to the plane of accretion discs have been discussed for several decades. recent simulations combining convection and the magnetorotational instability have given fresh impetus to the debate, as the interplay of the two processes can enhance angular momentum tr... | hydrodynamic convection in accretion discs |
during their thermally pulsing phase, asymptotic giant branch (agb) stars eject material that forms extended dusty envelopes1. visible polarimetric imaging found clumpy dust clouds within two stellar radii of several oxygen-rich stars2-6. inhomogeneous molecular gas has also been observed in multiple emission lines wit... | atmospheric molecular blobs shape up circumstellar envelopes of agb stars |
since identifying the gap in the h-r diagram (hrd) marking the transition between partially and fully-convective interiors, a unique type of slowly pulsating m dwarf has been proposed. these unstable m dwarfs provide new laboratories in which to understand how changing interior structures can produce potentially observ... | mind the gap. i. hα activity of m dwarfs near the partially/fully convective boundary and a new hα emission deficiency zone on the main sequence |
context. convective overshoot mixing is a critical ingredient of stellar structure models but is treated in most cases by ad hoc extensions of the mixing-length theory for convection. advanced theories that are both more physical and numerically treatable are needed.aims: convective flows in stellar interiors are highl... | stellar evolution models with overshooting based on 3-equation non-local theories. ii. main-sequence models of a- and b-type stars |
buoyancy-driven turbulent convection leads to a fully compressible flow with a prominent top-down asymmetry of first- and second-order statistics when the adiabatic equilibrium profiles of temperature, density and pressure change very strongly across the convection layer. the growth of this asymmetry and the formation ... | compressible turbulent convection in highly stratified adiabatic background |
this work is the first attempt to describe the multi-dimensional structure of accreting young stars based on fully compressible time implicit multi-dimensional hydrodynamics simulations. one major motivation is to analyse the validity of accretion treatment used in previous 1d stellar evolution studies. we analyse the ... | multi-dimensional structure of accreting young stars |
we present the evolution of massive star progenitors of supernovae of type iip. we take the example of the nearby and well-studied sn 2013ej. we explore how convective overshoot affects the stellar structure, surface abundances, and effective temperature of massive stars, using the modules for experiments in stellar as... | type iip supernova progenitors and their explodability. i. convective overshoot, blue loops, and surface composition |
we calculate the dynamical tides raised by a close planetary companion on non-rotating stars of 1 and 1.4 m⊙. using the henyey method, we solve the fully non-adiabatic equations throughout the star. the horizontal lagrangian displacement is found to be 10-100 times larger than the equilibrium tide value in a thin regio... | non-adiabatic tidal oscillations induced by a planetary companion |
we present a spectropolarimetric magnetic snapshot survey of 55 stars which includes 53 f-type stars ranging from spectral types f0 to f9 plus 2 chemically peculiar stars β crb, and δ cap. we look for magnetic fields in stars spanning a range of effective temperatures where the transition from fossil to dynamo magnetic... | a magnetic snapshot survey of f-type stars |
context. tidal interactions and planetary evaporation processes impact the evolution of close-in star-planet systems.aims: we study the impact of stellar rotation on these processes.methods: we compute the time evolution of star-planet systems consisting of a planet with an initial mass between 0.02 and 2.5 mjup (6 and... | star-planet interactions. vi. tides, stellar activity, and planetary evaporation |
we introduce here in the current research the revisiting of approach to the dynamics of sun center relative to barycenter of solar system by using self-resulting photo-gravitational force of the sun as the main reason of such motion. in case of slowly moving in the direction outwards with respect to the initial positio... | revisiting dynamics of sun center relative to barycenter of solar system or can we move towards stars using solar self-resulting photo-gravitational force? |
using magnetic field maps acquired by the helioseismic and magnetic imager on board the solar dynamics observatory, we measured rotation rates of 864 active and 322 ephemeral regions observed between 2010 and 2016. we found smaller magnetic tracers to show a tendency to rotate faster as compared to larger ones. thus, e... | the rotation rate of solar active and ephemeral regions - i. dependence on morphology and peak magnetic flux |
as the most abundant element in the universe after hydrogen and helium, oxygen plays a key role in planetary, stellar, and galactic astrophysics. its abundance is especially influential in terms of stellar structure and evolution, and as the dominant opacity contributor at the base of the sun's convection zone, it is c... | extended atomic data for oxygen abundance analyses |
convective overshooting in super asymptotic giant branch stars has been suggested to lead to the formation of hybrid white dwarfs with carbon-oxygen cores and oxygen-neon mantles. as the white dwarf cools, this core-mantle configuration becomes convectively unstable and should mix. this mixing has been previously studi... | mixing via thermocompositional convection in hybrid c/o/ne white dwarfs |
motivated by the dynamics in the deep interiors of many stars, we study the interaction between overshooting convection and the large-scale poloidal fields residing in radiative zones. we have run a suite of 3d boussinesq numerical calculations in a spherical shell that consists of a convection zone with an underlying ... | on the dynamical interaction between overshooting convection and an underlying dipole magnetic field - i. the non-dynamo regime |
we present measurements of spot properties on 31 young stellar objects, based on multiband data from the hoys (hunting outbursting young stars) project. on average the analysis for each object is based on 270 data points during 80 d in at least three bands. all the young low-mass stars in our sample show periodic photo... | a survey for variable young stars with small telescopes - vii. spot properties on ysos in ic 5070 |
we calculate the accretion mass of interstellar objects (isos) like `oumuamua on to low-mass population iii stars (pop. iii survivors), and estimate the surface pollution of pop. iii survivors. the iso number density estimated from the discovery of `oumuamua is so high (∼0.2 au-3) that pop. iii survivors have chances o... | metal pollution of low-mass population iii stars through accretion of interstellar objects like `oumuamua |
we present a local but fully nonlinear model of the solar tachocline, using three-dimensional direct numerical simulations. the tachocline forms naturally as a statistically steady balance between coriolis, pressure, buoyancy, and lorentz forces beneath a turbulent convection zone. uniform rotation is maintained in the... | a self-consistent model of the solar tachocline |
this study aims at investigating the ability of strong interactions between magnetic field concentrations during their rise through the convection zone to produce complex active regions at the solar surface. to do so, we perform numerical simulations of buoyant magnetic structures evolving and interacting in a model so... | interactions of twisted ω-loops in a model solar convection zone |
a better understanding of the amplitudes of stellar oscillation modes and surface granulation is essential for improving theories of mode physics and the properties of the outer convection zone of solar-like stars. a proper prediction of these amplitudes is also essential for appraising the detectability of solar-like ... | bolometric corrections of stellar oscillation amplitudes as observed by the kepler, corot, and tess missions |
convection in the cores of massive stars becomes anisotropic when they rotate. this anisotropy leads to a misalignment of the thermal gradient and the thermal flux, which, in turn, results in baroclinicity and circulation currents in the upper radiative zone. we show that this induces a much stronger meridional flow in... | enhanced rotational mixing in the radiative zones of massive stars |
using an analytic model, we derive the eigenfrequencies for thermal rossby waves that are trapped radially and latitudinally in an isentropically stratified atmosphere. we ignore the star's curvature and work in an equatorial f-plane geometry. the propagation of inertial waves is found to be sensitive to the relative d... | latitudinal propagation of thermal rossby waves in stellar convection zones |
we extend an existing born approximation method for calculating the linear sensitivity of helioseismic travel times to flows from cartesian to spherical geometry. this development is necessary for using the born approximation for inferring large-scale flows in the deep solar interior. as first sanity check, we compare ... | sensitivity kernels for flows in time-distance helioseismology: extension to spherical geometry |
context. surface differential rotation (sdr) plays a key role in dynamo models and determines a lower limit on the accuracy of stellar rotation period measurements. sdr estimates are therefore essential to constrain theoretical models and infer realistic rotation period uncertainties.aims: we measure a lower limit to s... | lower limit for differential rotation in members of young loose stellar associations |
we present results from an analytical model for magnetic buoyancy and rotational instabilities in full spherical shell stellar tachoclines that include rotation, differential rotation of either solar or antisolar type, and toroidal field. we find that in all cases, for latitudes where the tachocline vertical rotation g... | magnetic buoyancy and magnetorotational instabilities in stellar tachoclines for solar- and antisolar-type differential rotation |
in this paper, we present the results of three-dimensional numerical simulation of upward overshooting in turbulent compressible convection at large relative stability parameter s. similar to the previous simulations at small s, we find that the convectively stable zone can be partitioned into three layers: the thermal... | upward overshooting in turbulent compressible convection. ii. simulations at large relative stability parameters |
aims: in this study i assess how existing data for the solar analogues 16 cyg a and b, in particular the asteroseismic measurements obtained from kepler, constrain theoretical stellar models. the goal is two-fold: first to use these stars as benchmarks to discuss which precisions can realistically be expected on the in... | uncertainties and biases in modelling 16 cygni a and b |
context. solar gravity modes (g modes) are buoyancy waves that are trapped in the solar radiative zone and have been very difficult to detect at the surface. solar g modes would complement solar pressure modes (p modes) in probing the central regions of the sun, for example the rotation rate of the core.aims: a detecti... | signature of solar g modes in first-order p-mode frequency shifts |
within the convection zone of a rotating star, the presence of the coriolis force stabilizes long-wavelength convective modes. these modes, which would have been unstable if the star lacked rotation, are called overstable convective modes or thermal rossby waves. we demonstrate that the sun's rotation rate is sufficien... | overstable convective modes in a polytropic stellar atmosphere |
we report the first successful simulation of spontaneous formation of surface magnetic structures from a large-scale dynamo by strongly stratified thermal convection in cartesian geometry. the large-scale dynamo observed in our strongly stratified model has physical properties similar to those in earlier weakly stratif... | spontaneous formation of surface magnetic structure from large-scale dynamo in strongly stratified convection |
we compare 1d nonlocal turbulent convection models with 3d hydrodynamic numerical simulations. we study the validity of closure models and turbulent coefficients by varying the prandtl number, the péclet number, and the depth of the convection zone. four closure models of the fourth-order moments are evaluated with the... | numerical analysis of nonlocal convection—comparison with three-dimensional numerical simulations of efficient turbulent convection |
context. numerical simulations of magneto-convection have greatly expanded our understanding of stellar interiors and stellar magnetism. recently, fully compressible hydrodynamical simulations of full-star models have demonstrated the feasibility of studying the excitation and propagation of pressure and internal gravi... | toward fully compressible numerical simulations of stellar magneto-convection with the ramses code |
macroturbulence, introduced as a fudge to reproduce the width and shape of stellar absorption lines, reflects gas motions in stellar atmospheres. while in cool stars, it is thought to be caused by convection zones immediately beneath the stellar surface, the origin of macroturbulence in hot stars is still under discuss... | metallicity dependence of turbulent pressure and macroturbulence in stellar envelopes |
aims: we quantify the effect of observational spectroscopic and asteroseismic uncertainties on regularised least squares (rls) inversions for the radial differential rotation of sun-like and subgiant stars.methods: we first solved the forward problem to model rotational splittings plus the observed uncertainties for mo... | asteroseismic inversions for radial differential rotation of sun-like stars: sensitivity to uncertainties |
stably stratified layers are present in stellar interiors (radiative zones) as well as planetary interiors - recent observations and theoretical studies of the earth's magnetic field seem to indicate the presence of a thin, stably stratified layer at the top of the liquid outer core. we present direct numerical simulat... | magnetohydrodynamics of stably stratified regions in planets and stars |
we present an analysis of intermediate-dispersion spectra and photometric data of the newly identified cool, polluted white dwarf nltt 19868. the spectra obtained with x-shooter on the very large telescope-melipal show strong lines of calcium, and several lines of magnesium, aluminium and iron. we use these spectra and... | extreme abundance ratios in the polluted atmosphere of the cool white dwarf nltt 19868 |
mixing in the convective core is quite uncertain in core helium-burning stars. to explore the overshooting mixing beyond the convective core, we incorporated the k-ω proposed by li into the modules of experiments in stellar astrophysics (mesa), and investigated the overshooting mixing in evolution of subdwarf b (sdb) m... | convective overshooting in sdb stars using the k-ω model |
context. the reduced speed of sound technique (rsst) has been used for efficient simulation of low mach number flows in solar and stellar convection zones. the basic rsst equations are hyperbolic and are suitable for parallel computation by domain decomposition. the application of rsst is limited to cases in which dens... | semiconservative reduced speed of sound technique for low mach number flows with large density variations |
ozone is an important radiative trace gas in the earth's atmosphere and has also been detected on venus and mars. the presence of ozone can significantly influence the thermal structure of an atmosphere due to absorption of stellar uv radiation, and by this e.g. cloud formation. photochemical studies suggest that ozone... | effect of o3 on the atmospheric temperature structure of early mars |
characterizing stellar convection in multiple dimensions is a topic at the forefront of stellar astrophysics. numerical simulations are an essential tool for this task. we present an extension of the existing numerical tool-kit a-maze that enables such simulations of stratified flows in a gravitational field. the finit... | a well-balanced scheme for the simulation tool-kit a-maze: implementation, tests, and first applications to stellar structure |
we report on our 3d magnetohydrodynamic simulations of cylindrical weakly twisted flux tubes emerging from 18 mm below the photosphere. we perform a parametric study by varying the initial magnetic field strength (b 0), radius (r), twist (α), and length of the emerging part of the flux tube (λ) to investigate how these... | successful and failed flux tube emergence in the solar interior |
convective motions in the deep layers of the solar convection zone are affected by rotation, making the convective heat transport latitude-dependent, but this is not the case in the top layers near the surface. we use the thermal wind balance condition in the deeper layers to estimate the pole-equator temperature diffe... | a theoretical estimate of the pole-equator temperature difference and a possible origin of the near-surface shear layer |
stellar convection is a non-local process responsible for the transport of heat and chemical species. it can lead to enhanced mixing through convective overshooting and excitation of internal gravity waves (igws) at convective boundaries. the relationship between these processes is still not well understood and require... | impact of radial truncation on global 2d hydrodynamic simulations for a sun-like model |
we present results obtained from the studies of magnetic activities on four solar-type stars (f-type star kic 6791060, k-type star lo peg, and two m-type planet-hosting stars k2-33 and epic 211901114) by using optical observations from several ground- and space-based telescopes. in this study, we investigate magnetic a... | magnetic activities on active solar-type stars |
a rigorous and systematic computational and theoretical study, the first of its kind, for the laminar natural convective flow above rectangular horizontal surfaces of various aspect ratios ϕ (from 1 to ∞) is presented. two-dimensional computational fluid dynamic (cfd) simulations (for ϕ → ∞) and three-dimensional cfd s... | effects of finiteness on the thermo-fluid-dynamics of natural convection above horizontal plates |
context. the observation of gravity modes is expected to give us unprecedented insights into the inner dynamics of the sun. nevertheless, there is currently no consensus on their detection. within this framework, predicting their amplitudes is essential to guide future observational strategies and seismic studies.aims:... | amplitude of solar gravity modes generated by penetrative plumes |
one important ingredient of flux transport dynamo models is the rise of the toroidal magnetic field through the convection zone due to magnetic buoyancy to produce bipolar sunspots and then the generation of the poloidal magnetic field from these bipolar sunspots due to the babcock-leighton mechanism. over the years, t... | the treatment of magnetic buoyancy in flux transport dynamo models |
context. radial differential rotation is an important parameter for stellar dynamo theory and for understanding angular momentum transport.aims: we investigate the potential of using a large number of similar stars simultaneously to constrain their average radial differential rotation gradient: we call this "ensemble f... | asteroseismic inversions for radial differential rotation of sun-like stars: ensemble fits |
we show how magnetic observations of the sun can be used in conjunction with an axisymmetric flux-transport solar dynamo model in order to estimate the large-scale meridional circulation throughout the convection zone. our innovative approach rests on variational data assimilation, whereby the distance between predicti... | estimating the deep solar meridional circulation using magnetic observations and a dynamo model: a variational approach |
the process of convective settling is based on the assumption that a small fraction of the low-entropy downflows sink from the photosphere down to the bottom of the star's envelope convection zone retaining a substantial entropy contrast. we have previously shown that this process could explain the slow li depletion ob... | convective settling in main sequence stars: li and be depletion |
helioseismology has taught us a great deal about the stratification and kinematics of the solar interior, sufficient for us to embark upon dynamical studies more detailed than have been possible before. the most sophisticated studies to date have been the very impressive numerical simulations of the convection zone, fr... | some glimpses from helioseismology at the dynamics of the deep solar interior |
we derive the scaling of differential rotation in both slowly and rapidly rotating convection zones using order of magnitude methods. our calculations apply across stars and fluid planets and all rotation rates, as well as to both magnetized and purely hydrodynamic systems. we find shear |r∇ω| of order the angular freq... | convective differential rotation in stars and planets - i. theory |
we present 3d full star simulations, reaching up to 90% of the total stellar radius, for three 7 m ⊙ stars of different ages: zero-age main sequence (zams), mid-main sequence (midms), and terminal-age main sequence (tams). a comparison with several theoretical prescriptions shows that the generation spectra for all thr... | three-dimensional simulations of massive stars. ii. age dependence |
we attempt to determine the driver for clumping in hot-star winds by extending the measure of the spectral variability level of galactic wolf-rayet stars to by far the hottest known among them, the wn2 star wr 2 and the wo2 stars wr 102 and wr 142. these three stars have t⋆ = 140 and 200 kk, the last two being well abo... | clumping in the winds of wolf-rayet stars |
we study the role of non-linear effects on tidally excited internal gravity waves in stellar radiation zones in exoplanetary or binary systems. we are partly motivated to study tides due to massive short-period hot jupiters, which preferentially orbit stars with convective cores, for which wave breaking near the stella... | non-linear tidal excitation of superharmonic gravity waves in main-sequence stars in binary and exoplanetary systems |
a scheme of bayesian rotation inversion, which allows us to compute the probability of a model of a stellar rotational profile, is developed. the validation of the scheme with simple rotational profiles and the corresponding sets of artificially generated rotational shifts has been successfully carried out, and we can ... | bayesian rotation inversion of kic 11145123 |
we argue that the radiative zone above the iron core in pre-collapse cores of massive stars can store strong magnetic fields. to reach this conclusion, we use the stellar evolutionary code mesa to simulate the evolution of two stellar models with initial masses of mzams = 15 m⊙ and mzams = 25 m⊙, and reveal the entropy... | storing magnetic fields in pre-collapse cores of massive stars |
we carry out high-resolution calculations for the stellar convection zone. the main purpose of this letter is to investigate the effect of a small-scale dynamo on the differential rotation. the solar differential rotation deviates from the taylor-proudman state in which the angular velocity does not change along the ro... | breaking taylor-proudman balance by magnetic fields in stellar convection zones |
opacity enhancements for stellar interior conditions have been explored to explain observed pulsation frequencies and to extend the pulsation instability region for b-type main-sequence variable stars. for these stars, the pulsations are driven in the region of the opacity bump of fe-group elements at ∼200,000 k in the... | opacity effects on pulsations of main-sequence a-type stars |
in this paper, we have performed linear instability analysis of the penetrative convection for the boussinesq flow on a tilted f-plane. we have discussed the onset of instability as stationary and oscillatory convection. for the stationary convection, it has been shown that the penetration of convection is hindered by ... | penetrative convection for rotating boussinesq flow in tilted f-planes |
we study the combined effects of convection and radiative diffusion on the evolution of thin magnetic flux tubes in the solar interior. radiative diffusion is the primary supplier of heat to convective motions in the lower convection zone, and it results in a heat input per unit volume of magnetic flux tubes that has b... | effects of radiative diffusion on thin flux tubes in turbulent solar-like convection |
context. the different elemental abundances of the photosphere and the corona are striking features of not only the sun, but of other stars as well. this phenomenon is known as the first ionisation potential (fip) effect, and its strength can be characterized by the fip bias, the logarithmic abundance difference betwee... | extending the fip bias sample to magnetically active stars. challenging the fip bias paradigm |
context. about 0.2−2% of giant stars are li rich, that is to say their lithium abundance (a(li)) is higher than 1.5 dex. nearly 6% of these li-rich giant stars are super li rich, with an a(li) exceeding 3.2 dex. meanwhile, the formation mechanism of these li-rich and super li-rich giants is still under debate.aims: con... | li-rich and super li-rich giants produced by element diffusion |
the slowly pulsating b-type (spb) stars are the upper main-sequence stars on the hr diagram. their oscillations are high-order, low-degree g-mode and can be used to probe the structure of the radiative zone near the outer boundary of the convective core and constrain the chemical mixing in stellar interiors. in spb sta... | a new c-d-like diagram for spb stars: the variations of period spacing as a signature of evolutionary status |
the difference in stability of starspot distribution on the global and hemispherical scales is studied in the rotational spot variability of 1998 main-sequence stars observed by kepler mission. it is found that the largest patterns are much more stable than smaller ones for cool, slow rotators, whereas the difference i... | time-scales of stellar rotational variability and starspot diagnostics |
to explain the large‑scale magnetic field of the sun and other bodies, the mean‑field dynamo theory is commonly applied, where one solves the averaged equations for the mean magnetic field. however, the standard approach breaks down when the scale of the turbulent eddies becomes comparable to the scale of the variation... | strong nonlocality variations in a spherical mean‑field dynamo |
we present an investigation of the magnetic activity and flare characteristics of the subgiant stars mostly from f and g spectral types and compare the results with the main-sequence (ms) stars. the light curve of 352 stars on the subgiant branch (sgb) from the kepler mission is analyzed in order to infer stability, re... | flare activity and magnetic feature analysis of the flare stars. ii. subgiant branch |
context. the binary star α aurigae (otherwise known as capella) is extremely important to understanding the core hydrogen and helium burning phases of stars, as its primary star is likely evolving through the core helium burning phase. moreover, the masses of the star's two components are ∼2.5 m⊙ and ∼2.6 m⊙, meaning t... | an insight into capella (α aurigae): from the extent of core overshoot to its evolutionary history |
strong solar flares occur in δ-spots characterized by the opposite-polarity magnetic fluxes in a single penumbra. sunspot formation via flux emergence from the convection zone to the photosphere can be strongly affected by convective turbulent flows. it has not yet been shown how crucial convective flows are for the fo... | impact of subsurface convective flows on the formation of sunspot magnetic field and energy build-up |
magnetic flux generated and intensified by the solar dynamo emerges into the solar atmosphere, forming active regions (ars) including sunspots. existing theories of flux emergence suggest that the magnetic flux can rise buoyantly through the convection zone but is trapped at the photosphere, while its further rising in... | on the lorentz force and torque of solar photospheric emerging magnetic fields |
context. over 1500 dbz or dz white dwarfs (wds) have been observed so far, and polluted atmospheres with metal elements have been found among these wds. the surface heavy element abundances of known dbz or dz wds show an evolutionary sequence. cooling, diffusion, and accretion are important physical processes in wd evo... | formation, diffusion, and accreting pollution of db white dwarfs |
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